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samba_dnsupdate: make rodc_dns_update() more robust against timing problems

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Without this we had an interesting race!

The messaging_dgm code caches connected datagram sockets based on the
destination pid for 1 second.

The fact that samba_dnsupdate constantly recreates its messaging
context (and the underlying datagram socket) means that we the winbindd
messaging context may get a stale connection. As a result sending any
message from winbindd back to samba_dnsupdate will result in
ECONNREFUSED.

That means the IRPC response from winbindd never reaches
samba_dnsupdate, which will then hit a timeout.

In turn samba_dnsupdate on the RODC times out.

This was a workaround for the problem, by having just one global
IRPC handle and thus just one messaging_dgm context.
The actual problem is solved a few commits before
("messages_dgm: Properly handle receiver re-initialization").
But we keep this as an performance optimization, which hopefully
means that the overall samba_dnsupdate is less likely to
timeout after the hardcoded 20 seconds.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
This commit is contained in:
Stefan Metzmacher 2019-02-07 09:42:36 +01:00 committed by Andrew Bartlett
parent 767e60d973
commit 19f34b2161
1 changed files with 12 additions and 1 deletions
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13
source4/scripting/bin/samba_dnsupdate
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@ -633,6 +633,14 @@ def call_samba_tool(d, op="add", zone=None):
print("Failed 'samba-tool dns' based update: %s : %s" % (str(d), estr)) print("Failed 'samba-tool dns' based update: %s : %s" % (str(d), estr))
raise raise
irpc_wb = None
def cached_irpc_wb(lp):
global irpc_wb
if irpc_wb is not None:
return irpc_wb
irpc_wb = winbind.winbind("irpc:winbind_server", lp)
return irpc_wb
def rodc_dns_update(d, t, op): def rodc_dns_update(d, t, op):
'''a single DNS update via the RODC netlogon call''' '''a single DNS update via the RODC netlogon call'''
global sub_vars global sub_vars
@ -652,7 +660,7 @@ def rodc_dns_update(d, t, op):
netlogon.NlDnsGenericGcAtSite : netlogon.NlDnsDomainNameAlias netlogon.NlDnsGenericGcAtSite : netlogon.NlDnsDomainNameAlias
} }
w = winbind.winbind("irpc:winbind_server", lp) w = cached_irpc_wb(lp)
dns_names = netlogon.NL_DNS_NAME_INFO_ARRAY() dns_names = netlogon.NL_DNS_NAME_INFO_ARRAY()
dns_names.count = 1 dns_names.count = 1
name = netlogon.NL_DNS_NAME_INFO() name = netlogon.NL_DNS_NAME_INFO()
@ -680,6 +688,9 @@ def rodc_dns_update(d, t, op):
print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason)) print("Error setting DNS entry of type %u: %s: %s" % (t, d, reason))
error_count = error_count + 1 error_count = error_count + 1
if opts.verbose:
print("Called netlogon RODC update for %s" % d)
if error_count != 0 and opts.fail_immediately: if error_count != 0 and opts.fail_immediately:
sys.exit(1) sys.exit(1)